minor: Fix parquet pruning metrics display order (#18379)

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- Closes #.

## Rationale for this change

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It's better to let pruning metrics in parquet displayed in an order that
is the same as the actual pruning order:
```
metrics=...files_ranges_pruned_statistics=21 total → 3 matched, row_groups_pruned_statistics=1 total → 1 matched, row_groups_pruned_bloom_filter=1 total → 1 matched, page_index_rows_pruned=748901 total → 19813 matched...
```
Now it's ordered alphabetically.
See #18321 (comment)
for reproducing.

## What changes are included in this PR?

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is sometimes worth providing a summary of the individual changes in this
PR.
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Update the sort key API in `MetricValue`, to let the parquet pruning
metrics display in the expected order.

## Are these changes tested?
UT
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## Are there any user-facing changes?
No
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Author: 2010YOUY01

datafusion/core/tests/sql/explain_analyze.rs

@@ -860,6 +860,21 @@ async fn parquet_explain_analyze() {
         &formatted,
         "row_groups_pruned_statistics=1 total \u{2192} 1 matched"
     );
+
+    // The order of metrics is expected to be the same as the actual pruning order
+    // (file-> row-group -> page)
+    let i_file = formatted.find("files_ranges_pruned_statistics").unwrap();
+    let i_rowgroup_stat = formatted.find("row_groups_pruned_statistics").unwrap();
+    let i_rowgroup_bloomfilter =
+        formatted.find("row_groups_pruned_bloom_filter").unwrap();
+    let i_page = formatted.find("page_index_rows_pruned").unwrap();
+
+    assert!(
+        (i_file < i_rowgroup_stat)
+            && (i_rowgroup_stat < i_rowgroup_bloomfilter)
+            && (i_rowgroup_bloomfilter < i_page),
+            "The parquet pruning metrics should be displayed in an order of: file range -> row group statistics -> row group bloom filter -> page index."
+    );
 }
 
 // This test reproduces the behavior described in

datafusion/physical-plan/src/metrics/value.rs

@@ -749,17 +749,30 @@ impl MetricValue {
             Self::ElapsedCompute(_) => 1,
             Self::OutputBytes(_) => 2,
             // Other metrics
-            Self::PruningMetrics { .. } => 3,
-            Self::SpillCount(_) => 4,
-            Self::SpilledBytes(_) => 5,
-            Self::SpilledRows(_) => 6,
-            Self::CurrentMemoryUsage(_) => 7,
-            Self::Count { .. } => 8,
-            Self::Gauge { .. } => 9,
-            Self::Time { .. } => 10,
-            Self::StartTimestamp(_) => 11, // show timestamps last
-            Self::EndTimestamp(_) => 12,
-            Self::Custom { .. } => 13,
+            Self::PruningMetrics { name, .. } => match name.as_ref() {
+                // The following metrics belong to `DataSourceExec` with a Parquet data source.
+                // They are displayed in a specific order that reflects the actual pruning process,
+                // from coarse-grained to fine-grained pruning levels.
+                //
+                // You may update these metrics as long as their relative order remains unchanged.
+                //
+                // Reference PR: <https://github.com/apache/datafusion/pull/18379>
+                "files_ranges_pruned_statistics" => 3,
+                "row_groups_pruned_statistics" => 4,
+                "row_groups_pruned_bloom_filter" => 5,
+                "page_index_rows_pruned" => 6,
+                _ => 7,
+            },
+            Self::SpillCount(_) => 8,
+            Self::SpilledBytes(_) => 9,
+            Self::SpilledRows(_) => 10,
+            Self::CurrentMemoryUsage(_) => 11,
+            Self::Count { .. } => 12,
+            Self::Gauge { .. } => 13,
+            Self::Time { .. } => 14,
+            Self::StartTimestamp(_) => 15, // show timestamps last
+            Self::EndTimestamp(_) => 16,
+            Self::Custom { .. } => 17,
         }
     }